New research on validity and clinical utility of ICD‐11 vs. ICD‐10 and DSM‐5 diagnostic categories
Authors: Matteo Di  Vincenzo
Journal: World Psychiatry (2023)

A recent paper in World Psychiatry 1 summarized the recent literature on the validity and clinical utility of four new categories introduced in the ICD-11 chapter on mental disorders: complex post-traumatic stress disorder, prolonged grief disorder, gaming disorder, and compulsive sexual behaviour disorder. The reviewed evidence suggests that the new categories describe populations with clinically important features that were previously not recognized in the ICD classification, and that these po­pulations have specific treatment needs that would go unmet if the new disorders are not included in the classification. Moreover, the addition of the new categories has had a positive impact in terms of health reporting as well as development and testing of new interventionse.g., 2-4. In the past two years, there have been fur­ther studies focused on other ICD-11 cate­gories, testing their validity, clinical utility and/or interrater reliability in comparison with the corresponding categories in the ICD-10 and/or the DSM-55. Of special interest are four of these studies, dealing respectively with: a) the accuracy in diagnosing mood disorders depicted in case vignettes using ICD-11 vs. ICD-10 clinical descriptions and diagnostic guidelines6; b) the interrater reliability, concurrent validity, and clinical utility of the behavioural indicators introduced in the ICD-11 in order to improve the identification and treatment of individuals with disorders of intellectual development7; c) the sensitivity, specificity, and ability to predict the use of gender-affirming medical procedures of categories related to gender identity in the ICD-11 vs. DSM-58; d) the clinical utility of the formulation of irritability and oppositionality in youth which has been proposed by the ICD-11 compared with the corresponding ICD-10 and DSM-5 models9. The first of the above-mentioned studies6 reported that the use of ICD-11 guidelines, as compared with ICD-10 ones, allowed a more accurate detection of depressive episodes within the context of recurrent depressive disorder; led to lower rates of applying mood disorder diagnoses when none was warranted; and was associated with a less frequent misdiagnosis of depressive episodes as mixed depressive and anxiety disorder, or as prolonged grief disorder. However, some difficulties were found when differentiating between the ICD-11 categories of bipolar type I vs. type II disorder (a distinction not present in the ICD-10), and a poorer accuracy was observed when applying specifiers of se­verity of depression using the ICD-11 com­pared with the ICD-10 (a finding which has led to a revision of the ICD-11 severity specifiers for depressive episode). The study focusing on behavioural indicators for disorders of intellectual devel­op­ment7 found that these indicators had ex-­­­­­cel­lent interrater reliability (intra-class correlations between 0.91 and 0.97) and good to excellent concurrent validity (intra-class correlations between 0.66 and 0.82) across the four sites where the study was conduct­ed. Furthermore, these indicators were rat­ed as quick and easy to use and app­li­cable across levels of severity; and as useful for treatment selection, prognosis assessment, communication be­tween health care professionals, and education efforts. Finally, the indicators showed more diagnostic overlap between intellectual and adaptive functioning compared to standardized measures. The study on the validity of categories related to gender identity8 found that the sensitivity of the diagnostic requirements was equivalent in the ICD-11 (where these categories are not included in the chapter on mental disorders) and the DSM-5, but that the inclusion of the diagnostic re­quirements for distress and/or dysfunction in the DSM-5 is associated with a lower predictive power with respect to the use of gender-affirming medical procedures (i.e., history of hormone use and/or surgery). Furthermore, the ICD-11 diagnostic formulation was found to be more parsimonious and to contain more information about caseness than the DSM-5 model. The Internet-based field study on diagnostic classification of irritability and op­positionality in youth9, conducted with 196 clinicians from 48 countries, found that the formulation proposed in the ICD-11 (using chronic irritability as a qualifier for the diagnosis of oppositional defiant disorder) led to a more accurate identification of severe irritability and a better differentiation from boundary presentations compared to both the DSM-5 model (introducing the new category of disruptive mood dysregulation disorder) and the ICD-10 classification (listing oppositional defiant disorder as one of several conduct disorders without attention to irritability). Participants using the DSM-5 often failed to apply the diagnosis of disruptive mood dysregulation disorder when it was appropriate, and more frequently applied psychopathological diagnoses to irritability that was developmentally normative. Further studies based on the use of case vignettes in samples recruited from the World Health Organization (WHO) Global Clinical Practice Network – now including more than 17,800 clinicians from more than 160 countries (https://gcp.network) – are now ongoing. These studies, along with other investigations conducted in clinical settings and with the experience in the use of the ICD-11 worldwide10-16, will guide in the next few years possible refinements of the ICD-11 guidelines.